The displacements of the Earth’s surface before and after the earthquakes that took place near the southern shore of Lake Baikal on September 21, 2020 (Bystrinskoe earthquake with a magnitude of
M
= ...5.5), and August 27, 2008 (Kultukskoye earthquake with a magnitude of
M
= 6.3), were analyzed using satellite radar interferometry methods. Remote sensing data obtained by the Sentinel-1B (C-band) and the ALOS-1/2 PALSAR-1/2 (L-band) spaceborne synthetic aperture radars were used to study deformation processes. Blocks with different strain rates were found based on the results of analysis of satellite radar interferometric measurements for the period from May 2017 to October 2020 for the Bystrinskoe earthquake and from January 2007 to February 2011 for the Kultukskoe earthquake. The difference in the deformation values before the Bystrinskoe earthquake was 14 mm and that before the Kultukskoe earthquake ranged from 12 to 13 mm.
The article focuses on the way to determine the valid base settlement interval of the vertical steel tank with 20000 m3 capacity, which will provide reliable and trouble-free operation of the VST, ...taking into account the maximum possible upset distance of the pipeline in the gas equalizing system. In order to support the objectives of the research, it is proposed to perform process simulations of base settlement in a cylindrical steel tank with 20000 m3 capacity applying the software package ANSYS. A new model of the pipeline GES is designed, based on the tank model VST-20000, developed by the authors in 8. According to the results of a check calculation, the authors designed distribution diagrams of deformations and equivalent stresses in metal structures of the tank and elements of pipelines GES. Functional dependence of the equivalent stresses in metal structures on the value of base settlement VST is shown. The analysis of the received dependences found that upset distance ranging from 0 to 22mm provides a trouble-free and reliable operation of VST-20000.
Abstract
The paper proposes a variant of the algorithm for 3D numerical simulation of the rock mass stress-strain state in the vicinity of structural heterogeneities by the finite element method. ...Modeling of the stress-strain state is used, among other things, when analyzing the fractures in the rock mass, which can occur as a breakage or a shear along the weakening planes. The rock massif has a block structure, where the boundaries of various-scale blocks are structural disturbances of different orders. The surface planes of structural heterogeneities usually have complex geometry and spatial orientation, so the most adequate results can be obtained by 3D modeling of the disturbed rock mass. Besides, it is important to take into account the type of the stress-strain state, which can be not only gravitational, but also gravitational-tectonic, including horizontal loading of the rock mass. Accounting these features allows obtaining the most adequate geomechanical model of the studied object. For this purpose, the authors have studied and analyzed the existing approaches to modeling heterogeneities in the rock mass, including using the Goodman contact element, and developed its 3D modification. A mining engineer needs to have a handy tool that allows creating and editing a geomechanical model, taking into account mining plans and related sections. The model navigation, edition of its individual blocks to specify geology and creation of local sub-models make it necessary to use structured meshes of finite elements. Modification of the model with the introduction of contact elements entails the creation of an unstructured mesh, which complicates further manipulations with it. To solve this problem, a special zero element was developed, which allows saving a structured mesh format when implementing a contact element. This zero element, like the contact element, has zero thickness, and its nodes have averaged strength characteristics of adjacent blocks of the undisturbed rock mass. The result of these studies is a tool that allows creating 3D models of the rock mass stress-strain state, taking into account its structural heterogeneities and preserving the regular structure of the finite element mesh.
In the article, results of theoretical calculations of the piezoresistance characteristics of impurity germanene nanoribbons (NR) of the “arm-chair” type with donor defects with various ...concentrations uniformly distributed in the crystal lattice of the nanomaterial have been presented and analyzed. Arsenic atoms were used as donor impurities. Investigations of the NR’s band structure were carried out in the frameworks of the Hubbard’s and Anderson’s models. The computation of the main characteristic of the piezoresistance effect, i.e., the longitudinal component of the elastic conductivity tensor was carried out using the Green's function method within the framework of the same theoretical models. An analysis of the dependence of this characteristic on the tensile and compressive strains, the concentration of impurities and the nanoribbon width were carried out.
Stoping of potash seams during pillar mining is accompanied by deformations in underworked rock mass and the destruction of roof rocks and floors of mine workings in the extraction pillars of ...longwall faces. This type of mining can also cause sudden caving of the roof and seam floor in an extraction pillar of a longwall face, thus posing a threat to miners, leading to unplanned stoppages of mining operations and reducing the efficiency of mining. In addition, during the advance of a longwall face, subsidence of the soil surface occurs. It is therefore important to study the deformation of the soil surface and find ways of predicting this during the underground mining of potash seams. To evaluate the stress-strain state of the rock mass during longwall mining, a geomechanical model of potash seam mining was constructed under conditions of slice mining. This model took into account the main structural features of the underworked mass, and the caving of the roof of an underworked seam with filling of the worked-out longwall face and the opening of clay contacts in the salt stratum during mining operations. The results of mathematical modelling showed that a localised area of plastic deformation is formed in the soil, which is associated with the formation of opening mode fractures. At the same time, caving of the roof rock and simultaneous filling of the worked-out space take place, preventing further development of the rock jointing zones. The properties of the rocks from the caved roof determine the nature of this mass deformation. By varying these properties, we were able to achieve acceptable agreement between the estimated subsidence and field observations of the displacement of the earth surface. A comparative analysis of the estimated and actual subsidence shows that in order to yield an accurate description of the mass deformation, softening of the caved rocks should not take place immediately to give the final values of the deformation properties, but should change over time.
Стремление к уменьшению массы машин и конструкций при улучшении их качества, а также к наиболее полному использованию механических свойств материалов требует постоянного совершенствования и развития ...известных методов расчета и анализа напряженно-деформированного состояния материалов в условиях ползучести.
В статье предлагается численный метод оценивания характеристик третьей стадии неизотермической ползучести по совокупности диаграмм ползучести, построенных при обработке результатов испытаний для различных значений номинального напряжения и температур.
В основе метода лежат нелинейные регрессионные модели, среднеквадратичные оценки параметров которых находятся посредством линеаризации, в том числе на основе разностных уравнений, описывающих результаты наблюдений.
Предлагаемый численный метод может быть также использован для оценки параметров третьей стадии ползучести, когда результаты эксперимента в форме совокупности диаграмм испытаний представлены только для одной температуры.
Приведены результаты апробации разработанного численного метода при обработки результатов эксперимента в форме диаграмм ползучести сплава 09Г2С при различных температурах.
Достоверность и эффективность представленных в работе алгоритмов вычислений и методов нелинейного оценивания подтверждаются результатами численно-аналитических исследований и построенными на основе экспериментальных данных математическими моделями третьей стадии неизотермической ползучести.
The desire to reduce the mass of machines and structures while improving their quality, as well as to make the most complete use of the mechanical properties of materials, requires permanent improvement and development of known methods for calculating and analyzing the stress-strain state of materials under creep conditions.
The article proposes a numerical method for estimating the characteristics of the third stage of non-isothermal creep based on a set of creep diagrams constructed when processing test results for various values of nominal stress and temperature.
The method is based on the nonlinear regression model, the root-mean-square estimates of the parameters of which are found by linearization, including on the basis of difference equations describing the experimental results. The proposed numerical method can also be used to estimate the parameters of the third creep stage, when the experimental results are presented in the form of a set of test diagrams for only one temperature.
The results of testing the developed numerical method for processing the experimental results in the form of creep diagrams for the 09G2C alloy at different temperatures are presented.
The reliability and efficiency of the calculation algorithms and methods of nonlinear estimation presented in the work are confirmed by the results of numerical and analytical studies and mathematical models of the third stage of non-isothermal creep constructed on the basis of experimental data.
Aim of research - to continue the development of methods for determining the stress-strain state of rods during torsion using materials resistance methods. Methods. A new approach for determining ...tangential torsional stresses for arbitrary cross sectional rods, based on simplified assumptions of material resistance, is proposed. The main feature of this approach is the approximation of rectangular or any complex cross section of reinforced concrete structures by describing a large circle around the cross section and splitting it into small squares with circles inscribed into them. Results. Three theorems have been formulated, the first of which relates the accumulation of tangential stresses (increments) from the edges of a rectangle to the middle of a rectangular section with the formula for determining tangent stresses for round sections. The second theorem allows to establish a connection between the tangential stresses calculated for each of the small squares-circles and the tangent stresses of the large circle through their increments. The third theorem makes it possible to find tangential stresses for each of the small square circles. The proposed approach allows to remove the need to use special tables for the calculation and not only in the elastic stage. It also makes it possible to separate the stress-strain state in the whole set of round cross-sections from the additional field caused by the deplanation of the rectangular cross-section. In addition, the proposed approach makes it possible to take into account the concentration of angular deformations in the incoming angles and other places with changing geometric parameters.
The need for reliable supports for locating and maintaining the equipment of cellular opera-tors is increasing every year. The classic version of the supports are lattice towers. At present, ...optimization of the parameters of lattice towers, which is one of the ways to improve the efficiency of their design and construction, is of great importance. The purpose of the work is chosen definition of a rational constructive form of lattice cellular communication towers. In the work, the calculation and analysis of the tower supports of a prismatic and pyramidal form are made with varying basic geometric parameters of the structure and the ratio of parameters between them. To create basic dependencies, numerical modeling methods are used. According to the results of a critical analysis of the literature on the calculation of lattice supports of high-rise buildings, the absence of recommended optimal values of the geometric parameters of structures and the relationship between them was established. The stress-strain state of the design models of lattice towers of a prismatic and pyramidal shape was assessed with variation of the main overall geometric parameters of the structures. To achieve the goal of finding a rational structural form of lattice supports, two rationalization criteria have been tested and applied - the simultaneous fulfillment of the requirements of both limiting states and minimization of the mass of the structure. The results of the study of lattice tower supports are presented in dimensionless parameters, which can be applied by the engineer when assigning the overall dimensions of the structure at the initial design stage.
For transportation of dangerous goods rail transport uses tank wagons. Structural changes can contribute to reduction in the maximum stresses, and as a result, to improvement in technical and ...economic characteristics of a tank wagon. In order to investigate the stress-strain state of a tank wagon the finite element model was built, its adequacy having been checked by results of analytical calculations and experiments. It has been applied for numerous researches to find the most effective bracket support structure by comparing it to the existing structure. The laws of stiffness change in radial direction and the laws of contact pressure change have been demonstrated. The improved structure has been checked by a load spectrum according to normative documents.
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